Optical pick up and optical disc device having optical shield for suppressing the influence of stray light through hologram element

Abstract

An optical pickup according to the present invention includes: a light source 1 d for irradiating an optical disk 4 with light; a lens 3 for converging the light onto the optical disk 4 ; a photodetector 1 c having a plurality of detection regions 1 cf, 1 ct for detecting light which is reflected from a signal surface of the optical disk 4 and converting the light into an electrical signal; a hologram element 1 a having a hologram region 1 b for guiding the reflected light to the photodetector 1 c ; and a light-shielding plate 2 for blocking at least a portion of light transmitted through a region of the hologram element 1 a other than the hologram region 1 b . The light-shielding plate 2 includes a light shielding portion 2 b for blocking light, and an aperture 2 a for allowing the light to be transmitted therethrough. The aperture 2 b is present, above an upper face of the hologram element 1 a , in a region including the hologram region 1 b , and a center position of the aperture 2 b is shifted from a center position of the hologram region 1 b.

1. An optical pickup comprising:
 a light source for irradiating an optical disk with light; 
 a lens for converging the light onto the optical disk; 
 a photodetector having a plurality of detection regions for detecting light which is reflected from a signal surface of the optical disk and converting the light into an electrical signal; 
 a hologram element having a hologram region for guiding the reflected light to the photodetector; and 
 an optical shield for blocking at least a portion of light transmitted through a region of the hologram element other than the hologram region, wherein, 
 the optical shield includes a light shielding portion for blocking the reflected light, and an aperture for allowing the reflected light to be transmitted therethrough; and 
 the aperture of the optical shield is present, above an upper face of the hologram element, in a region including the hologram region, and a center position of the aperture is shifted from a center position of the hologram region; and 
 the plurality of detection regions of the photodetector include tracking error signal detection regions and focus error signal detection regions; and 
 the light shielding portion of the optical shield traverses lines extending from a convergence point of the light on the optical disk to center portions of the respective tracking error signal detection regions, and does not traverse at least one of lines extending from the convergence point of the light on the optical disk to center portions of the respective focus error signal detection regions. 
 
     
     
       2. The optical pickup of  claim 1 , wherein the optical shield is in contact with or close to the upper face of the hologram element. 
     
     
       3. The optical pickup of  claim 1 , wherein,
 the light source and the photodetector are supported on a same substrate and compose a unit; and 
 the hologram element is fixed on the unit. 
 
     
     
       4. The optical pickup of  claim 1 , wherein,
 the hologram element includes a grating region formed on a lower face thereof, the grating region diffracting the light which is emitted from the light source to form two subbeams for a tracking error signal, and transmitting the light to form a main beam; and 
 the hologram region causes the subbeams reflected from the optical disk to be guided to the tracking error signal detection regions, and causes the main beam reflected from the optical disk to be guided to the focus error signal detection regions. 
 
     
     
       5. The optical pickup of  claim 1 , wherein the hologram element includes a rib for restricting movement of the optical shield. 
     
     
       6. The optical pickup of  claim 1 , wherein the optical shield includes a pull knob. 
     
     
       7. The optical pickup of  claim 1 , wherein the optical shield is formed of a resin or a metal. 
     
     
       8. The optical pickup of  claim 1 , wherein the optical shield is of a sheet shape. 
     
     
       9. The optical pickup of  claim 1 , wherein the optical shield is printed on the upper face of the hologram element. 
     
     
       10. The optical pickup of  claim 1 , wherein the optical shield is composed of ink which is applied on the upper face of the hologram element. 
     
     
       11. An optical disk apparatus comprising a motor for rotating an optical disk and an optical pickup for optically reading information which is recorded on the optical disk,
 the optical pickup including: 
 a light source for irradiating an optical disk with light; 
 a lens for converging the light onto the optical disk; 
 a photodetector having a plurality of detection regions for detecting light which is reflected from a signal surface of the optical disk and converting the light into an electrical signal; 
 a hologram element having a hologram region for guiding the reflected light to the photodetector; and 
 an optical shield for blocking at least a portion of light transmitted through a region of the hologram element other than the hologram region, wherein, 
 the optical shield includes a light shielding portion for blocking the reflected light, and an aperture for allowing the reflected light to be transmitted therethrough; and 
 the aperture of the optical shield is present, above an upper face of the hologram element, in a region including the hologram region, and a center position of the aperture is shifted from a center position of the hologram region; and 
 the plurality of detection regions of the photodetector include tracking error signal detection regions and focus error signal detection regions; and 
 the light shielding portion of the optical shield traverses lines extending from a convergence point of the light on the optical disk to center portions of the respective tracking error signal detection regions, and does not traverse at least one of lines extending from the convergence point of the light on the optical disk to center portions of the respective focus error signal detection regions.